1. Field of the Invention
This invention relates to a multiple speed ratio tractor transmission. More particularly, the invention pertains to a hydraulically actuated mechanism to engage the creeper speed gear ratios of the transmission.
2. Description of the Prior Art
Tractor transmissions are designed to produce a larger number of gear ratios within a mechanism located between the engine and the final drive or differential mechanism. In the conventional design, the gear arrangement of the transmission may produce a gear reduction or ratio of approximately 9:1 between the speed of the transmission output and the engine speed. Typically, the torque delivery path of a tractor transmission includes a creeper speed mechanism located behind the transmission gear arrangement and before the differential mechanism. The creeper speed mechanism produces an additional speed reduction of about 5:1 between the output of the transmission gear arrangement and the output of the creeper speed mechanism. This combination of speed ratios will produce an overall speed reduction of approximately 45:1 between the output of the creeper speed mechanism and the engine.
Because the creeper speed mechanism is an additional gear mechanism located in conventional tractor drivelines at the rear of the transmission, its presence increases the overall length of the transmission. It is preferable that the creeper speed mechanism be as short as possible so that the transmission can be fitted within the smallest space possible. Yet to produce a sufficiently large speed reduction between the engine and the transmission output required by tractor operators for certain conditions, the creeper speed mechanism must include several speed reductions which necessarily increase the space required by the mechanism.